Danario Alexander's left knee has given him a lifetime of challenges. Now the other knee presents what perhaps will be his biggest obstacle yet.

The San Diego Chargers announced Tuesday that Alexander tore the ACL in his right knee. It is highly likely the injury will require season-ending surgery.

It's a cruel blow for Alexander, who has endured at least five surgeries on his left knee dating to his college days. The latest injury came during Tuesday's practice. Chargers coach Mike McCoy had downplayed the seriousness of the injury.

Alexander emerged as an impact player in the back end of last season, finishing with seven touchdowns while averaging nearly 18 yards per catch. He was slotted to be the Chargers' No. 1 wide receiver this season.